SU381145A1 - DEVICE TO CONTROL T-PHASE DIRECT FREQUENCY CONVERTER - Google Patents

Description

one

Devices are known for controlling indirectly frequency converters, comprising a modulating voltage generator, a separate control unit, and a square pulse generator.

The described device differs from the known ones in that it is equipped in each output phase with a modulator, a phase-sensitive demodulator and a high-frequency phase inverter, with one input of the demodulator through the modulator connected to the output of the modulating voltage generator and the second input through the phase inverter the high frequency is connected to the separate control unit, and the additional inputs of the modulator and phase inverter are connected to the output of the square pulse generator.

This makes it possible to increase the symmetry of the generation of control pulses and, consequently, improve the energy quality of the output voltage of the converter.

FIG. 1 is a block diagram of a converter control device; in fig. 2 shows timing diagrams illustrating the operation of the device.

The described device contains a three-phase modulating voltage generator /, the main outputs of which are connected to the inputs of modulators 2 controlled from

windings of the generator 3 rectangular pulses, three high-frequency phase inverters 4, controlled from the windings of the generator 3 and the corresponding separate control blocks 5; three modulators 6, the inputs of which are connected to the outputs of modulator 2, and the control circuits - to the outputs of high-frequency phase inverters 4; three comparison circuits 7, the inputs of which are connected to the outputs of the demodulators

6 and to the output of the sawtooth voltage generator 8 controlled by the polarity sensor of the input voltage 9; three phase modulators 10, the inputs of which are connected to the outputs of the comparison circuits 7; three distributors // imulses, to the inputs of which signals are provided from the outputs of phase modulators 10, protective impulse formation unit 12, separate control units 5, and linearity sensors 9; three blocks of output stages 13, producing impulses of control of the required shape and power, the outputs of which are connected to the control of the electrodes of the converter valves; three sensors of conductivity of valve sets

14; three separate control devices 5, to the inputs of which, through the coincidence circuits, are connected the outputs of the conductivity sensors of the valve sets 14 and the outputs of the selector pulses of the modulating generator

voltage.

The device works as follows.

The three-phase modulating voltage generator / with linear electric correction by nair and frequency generates three 120 ° sinusoidal voltages shifted by the known methods and the selector pulses corresponding to the positive and negative half-waves of these voltages.

Sinusoidal voltages from the output of 5 blocks / Converted by block 2 to high-frequency voltages amplified by the output (low) frequency (Fig. 2e), the frequency of the high-frequency filling (Fig. 2e) being determined by the generator 3 and much higher than the upper value of the output (low) frequency . The voltage from the output of the modulator 2 is fed to the input of the block 6, controlled from the high-frequency phase inverter 4B by the block 4 according to commands from the separate control unit 5, the phase of the switching signals controlling the operation of the demodulator 6 is reversed when the load current polarity changes (Fig. 2, h, i, k). At the output of block 6, this is distinguished in the form of sinusoid sections of a smooth modulating voltage component (Fig. 2e). As a result of comparison, at the input of block 7 obtained by a "smooth modulating voltage component with a reference sawtooth voltage (Fig. 2l), the phase modulator Yu produces pulses (Fig. 2m), which, together with the protective pulses produced by block 12, arrive pulse distributor / A

Thus, the use of high-frequency filling of the modulating signal and control of the modulators (phase-sensitive rectifiers) by the commands of the blocks 5 allows to provide a range of change of the switching angle of the valves O-180 ° using one matching device and a phase modulator for each output phase of the converter that eliminates asymmetry in control pulse generation. In addition, the use of high-frequency filling facilitates the matching of the generator with other devices of the control system, eliminates the appearance of a constant component in the modulating voltage and facilitates, in necessary cases, the propagation of block signals using small-sized high-frequency transformers.

Synchronization of the sawtooth generator (reference) voltage S with the mains

it is controlled by a polarity sensor 9 (Fig. 2 a, b, c, d), which simultaneously controls the operation of unit 12, which provides for the generation of protective impulses B moments 180 ° —p. ((Serials - minimum required angle of advance when the converter is operating in an inverter mode.) With this method of forming a sawtooth voltage, matching the output of block 8 with the input of block 7 is easily carried out with P; transformer power, which simultaneously excludes the appearance of a constant component, in its own voltage. control Effects 5 ensures the separate operation of sets by acting on a pulse distributor. The operation of unit 5 is carried out from conductivity sensors of valve sets 14 based on voltage measurement on converter valves. reliability of the system as a whole. At the same time, to select the output from the operation of the set, selector pulses are used, which correspond to voltage. It should be noted that the use of selector pulses ensures the absence of multiple switching of valve kits in the discontinuous current mode. The pulses from the distributor output are amplified in power by the output stages 13 and are applied to the valves.

Subject invention

A device for controlling and direct phase frequency converter, comprising a modulating voltage generator, a separate control unit and a generator of right-angle pulses, characterized in that, in order to improve the symmetry of the control pulses, it is equipped with an modulator, phase-sensitive demodule in the output phase a torus and a high frequency phase inverter, with one demodulator input through a modulator connected to the output of a modulating voltage generator, the second input through a high frequency phase inverter is connected to separate control units, and additional inputs of the modulator and phase inverter are connected to the output of the square-wave generator.

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